Definitions of intangible:

• noun:   assets that are saleable though not material or physical
• adjective:   hard to pin down or identify

  Example: "An intangible feeling of impending disaster"

• adjective:   incapable of being perceived by the senses especially the sense of touch

  Example: "The intangible constituent of energy- James Jeans"

• adjective:   (of especially business assets) not having physical substance or intrinsic productive value

  Example: "Intangible assets such as good will"

• adjective:   lacking substance or reality; incapable of being touched or seen

  Example: "That intangible thing--the soul"